I improved the performance of code that determines the legality of pseudo-legal moves. Previously, move legality was tested prior to playing a move. This consisted of playing a move (to test whether it exposed its own king to check and whether it delivered check on the enemy king), undoing the move, updating the “check” move property, then re-playing the move. Now a move is played, move legality and check is tested, and the Board.PlayMove method returns a (bool isLegal, bool deliversCheck) tuple.
The calling method (such as Search.GetDynamicScore or Search.GetQuietScore) then either 1) undoes the move (if illegal or futile) and continues to the next pseudo-legal move or 2) searches the resulting position.
In addition to move legality, I experimented with other performance improvements. None of these experiments succeeded except PR 33: Trust Move Capture Victim, which eliminated redundant calls to Position.GetPiece(Square square) in move generation and when playing moves.
Eliminating redundant double-playing of a move (to test move legality) during search increased the search speed of MadChess 3.1 Beta and produced a 36 Elo gain in playing strength.
| Feature | Category | Date | Commit1 | WAC2 | Elo Rating3 | Improvement |
|---|---|---|---|---|---|---|
| Move Legality Performance Improvement |
Search | 2022 Mar 18 | 533e382 | 289 | 2687 | +36 |
| Pawn Structure | Evaluation | 2022 Jan 11 | d691b32 | 288 | 2651 | +15 |
| Threats | Evaluation | 2021 Oct 24 | 26e5323 | 289 | 2636 | +7 |
| Color-Agnostic Code | Evaluation | 2021 Sep 13 | 2b475bc | 286 | 2629 | +12 |
| Singular Move | Search | 2021 Jun 14 | 0c601ea | 290 | 2617 | +13 |
| Endgame Eval Scaling | Evaluation | 2021 Apr 08 | 4d22dec | 286 | 2604 | +12 |
| Bishop Pair | Evaluation | 2021 Mar 14 | 2960ec9 | 285 | 2592 | +22 |
| Position Cache Optimization | Search | 2021 Feb 23 | 42d7702 | 286 | 2570 | +8 |
| Move Generation Optimization | Search | 2021 Feb 17 | 22002dc | 287 | 2562 | +12 |
| PVS and Null Move | Search | 2021 Feb 09 | f231dac | 285 | 2550 | +20 |
| Remove Aspiration Windows | Search | 2020 Dec 20 | 4b7963b | 290 | 2530 | +9 |
| Time Management | Search | 2020 Dec 19 | d143bb5 | 286 | 2521 | +8 |
| Crash Bug | Search | 2020 Aug 29 | 2d855ec | 288 | 2513 | +0 |
| King Safety | Evaluation | 2020 Aug 16 | 6794c89 | 288 | 2513 | +63 |
| Eval Param Tuning | Evaluation | 2020 Jul 23 | bef88d5 | 283 | 2450 | +30 |
| Late Move Pruning | Search | 2020 Feb 08 | 6f3d17a | 288 | 2420 | +29 |
| Piece Mobility | Evaluation | 2020 Feb 01 | 5c5d4fc | 282 | 2391 | +62 |
| Passed Pawns | Evaluation | 2018 Dec 27 | 103 | 279 | 2329 | +119 |
| Staged Move Generation | Search | 2018 Dec 15 | 93 | 275 | 2210 | +39 |
| History Heuristics | Search | 2018 Dec 03 | 84 | 275 | 2171 | +28 |
| Eval Param Tuning | Evaluation | 2018 Nov 24 | 75 | 272 | 2143 | +47 |
| Sophisticated Search Material and Piece Location |
Baseline | 2018 Nov 08 | 58 | 269 | 2096 | 0 |
- GitHub commit (hash) or Subversion source code revision (integer)
- Win At Chess position test, 3 seconds per position
- Bullet chess, 2 min / game + 1 sec / move
I work as a Software Architect at an insurance company. We're building a modern tech stack in the cloud using C#, Azure, ASP.NET Core, Angular, TypeScript, etc.